Incorrect module part number for the vehicle

A control module has been fitted that is not the variant this vehicle expects — a superseded part number, one from a different market or model year, or one whose software does not match the rest of the car.

Modern vehicles check. Modules exchange identification on startup and compare it against what the configuration says should be there, so a mismatch is usually reported rather than silently tolerated. That check exists because a module is not a generic box: the same physical part can carry calibration for different engines, different markets, different equipment levels.

Second-hand parts are the commonest route in, and the reason is understandable — a used module is a fraction of a new one. But a used module usually arrives carrying the previous vehicle's configuration, and on many designs it must be coded to the new car before it will work correctly. Some are locked to the donor outright and cannot be transferred at all.

The symptoms are what make this hard to recognise, because it rarely fails cleanly. A mismatched module often works — badly. Features missing that the car should have, a function behaving as it would on a different model, or faults that make no sense against the wiring diagram, because the module believes it is fitted to something else.

Two things to establish before chasing anything downstream. Whether the part number matches what the vehicle's build record specifies, and whether the module was coded or programmed after fitting. A great deal of diagnostic time is spent on faults that are really a module answering questions about a different car — and on an electrified vehicle the stakes are higher, because a battery or charging module configured for the wrong pack is making decisions about voltages and currents on the basis of the wrong numbers.